First, thank you for reporting this issue to us and providing us the information to help find the cause of the problem.
Second, sorry for the slow response, but I do have good news. We've addressed the issue that was preventing you from charging the new saved/updated card. So now you or the customer can pay the two membership invoices you mentioned with the saved card on file.
You can simply go to the order and pay the order, since the customer has already updated the new card, this time when you charge the saved card, it should charge the updated card correctly without declining.
If you have any more questions, or are still unable to pay the orders with the saved card for some reason, please let me know!